new generic FFT/MDCT code for audio codecs

Originally committed as revision 1088 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 229 insertions, 0 deletions

diff --git a/libavcodec/fft.c b/libavcodec/fft.c
new file mode 100644
index 0000000000..0f5181ac3c
--- /dev/null
+++ b/libavcodec/fft.c
@@ -0,0 +1,229 @@
+/*
+ * FFT/IFFT transforms
+ * Copyright (c) 2002 Fabrice Bellard.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+#include "dsputil.h"
+
+/**
+ * The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is
+ * done 
+ */
+int fft_init(FFTContext *s, int nbits, int inverse)
+{
+    int i, j, m, n;
+    float alpha, c1, s1, s2;
+    
+    s->nbits = nbits;
+    n = 1 << nbits;
+
+    s->exptab = av_malloc((n / 2) * sizeof(FFTComplex));
+    if (!s->exptab)
+        goto fail;
+    s->revtab = av_malloc(n * sizeof(uint16_t));
+    if (!s->revtab)
+        goto fail;
+    s->inverse = inverse;
+
+    s2 = inverse ? 1.0 : -1.0;
+        
+    for(i=0;i<(n/2);i++) {
+        alpha = 2 * M_PI * (float)i / (float)n;
+        c1 = cos(alpha);
+        s1 = sin(alpha) * s2;
+        s->exptab[i].re = c1;
+        s->exptab[i].im = s1;
+    }
+    s->fft_calc = fft_calc_c;
+    s->exptab1 = NULL;
+
+    /* compute constant table for HAVE_SSE version */
+#if defined(HAVE_MMX) && 0
+    if (mm_flags & MM_SSE) {
+        int np, nblocks, np2, l;
+        FFTComplex *q;
+
+        np = 1 << nbits;
+        nblocks = np >> 3;
+        np2 = np >> 1;
+        s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex));
+        if (!s->exptab1)
+            goto fail;
+        q = s->exptab1;
+        do {
+            for(l = 0; l < np2; l += 2 * nblocks) {
+                *q++ = s->exptab[l];
+                *q++ = s->exptab[l + nblocks];
+
+                q->re = -s->exptab[l].im;
+                q->im = s->exptab[l].re;
+                q++;
+                q->re = -s->exptab[l + nblocks].im;
+                q->im = s->exptab[l + nblocks].re;
+                q++;
+            }
+            nblocks = nblocks >> 1;
+        } while (nblocks != 0);
+        av_freep(&s->exptab);
+    }
+#endif
+
+    /* compute bit reverse table */
+
+    for(i=0;i<n;i++) {
+        m=0;
+        for(j=0;j<nbits;j++) {
+            m |= ((i >> j) & 1) << (nbits-j-1);
+        }
+        s->revtab[i]=m;
+    }
+    return 0;
+ fail:
+    av_freep(&s->revtab);
+    av_freep(&s->exptab);
+    av_freep(&s->exptab1);
+    return -1;
+}
+
+/* butter fly op */
+#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
+{\
+  FFTSample ax, ay, bx, by;\
+  bx=pre1;\
+  by=pim1;\
+  ax=qre1;\
+  ay=qim1;\
+  pre = (bx + ax);\
+  pim = (by + ay);\
+  qre = (bx - ax);\
+  qim = (by - ay);\
+}
+
+#define MUL16(a,b) ((a) * (b))
+
+#define CMUL(pre, pim, are, aim, bre, bim) \
+{\
+   pre = (MUL16(are, bre) - MUL16(aim, bim));\
+   pim = (MUL16(are, bim) + MUL16(bre, aim));\
+}
+
+/**
+ * Do a complex FFT with the parameters defined in fft_init(). The
+ * input data must be permuted before with s->revtab table. No
+ * 1.0/sqrt(n) normalization is done.  
+ */
+void fft_calc_c(FFTContext *s, FFTComplex *z)
+{
+    int ln = s->nbits;
+    int	j, np, np2;
+    int	nblocks, nloops;
+    register FFTComplex *p, *q;
+    FFTComplex *exptab = s->exptab;
+    int l;
+    FFTSample tmp_re, tmp_im;
+
+    np = 1 << ln;
+
+    /* pass 0 */
+
+    p=&z[0];
+    j=(np >> 1);
+    do {
+        BF(p[0].re, p[0].im, p[1].re, p[1].im, 
+           p[0].re, p[0].im, p[1].re, p[1].im);
+        p+=2;
+    } while (--j != 0);
+
+    /* pass 1 */
+
+    
+    p=&z[0];
+    j=np >> 2;
+    if (s->inverse) {
+        do {
+            BF(p[0].re, p[0].im, p[2].re, p[2].im, 
+               p[0].re, p[0].im, p[2].re, p[2].im);
+            BF(p[1].re, p[1].im, p[3].re, p[3].im, 
+               p[1].re, p[1].im, -p[3].im, p[3].re);
+            p+=4;
+        } while (--j != 0);
+    } else {
+        do {
+            BF(p[0].re, p[0].im, p[2].re, p[2].im, 
+               p[0].re, p[0].im, p[2].re, p[2].im);
+            BF(p[1].re, p[1].im, p[3].re, p[3].im, 
+               p[1].re, p[1].im, p[3].im, -p[3].re);
+            p+=4;
+        } while (--j != 0);
+    }
+    /* pass 2 .. ln-1 */
+
+    nblocks = np >> 3;
+    nloops = 1 << 2;
+    np2 = np >> 1;
+    do {
+        p = z;
+        q = z + nloops;
+        for (j = 0; j < nblocks; ++j) {
+            BF(p->re, p->im, q->re, q->im,
+               p->re, p->im, q->re, q->im);
+            
+            p++;
+            q++;
+            for(l = nblocks; l < np2; l += nblocks) {
+                CMUL(tmp_re, tmp_im, exptab[l].re, exptab[l].im, q->re, q->im);
+                BF(p->re, p->im, q->re, q->im,
+                   p->re, p->im, tmp_re, tmp_im);
+                p++;
+                q++;
+            }
+
+            p += nloops;
+            q += nloops;
+        }
+        nblocks = nblocks >> 1;
+        nloops = nloops << 1;
+    } while (nblocks != 0);
+}
+
+/**
+ * Do the permutation needed BEFORE calling fft_calc()
+ */
+void fft_permute(FFTContext *s, FFTComplex *z)
+{
+    int j, k, np;
+    FFTComplex tmp;
+    const uint16_t *revtab = s->revtab;
+    
+    /* reverse */
+    np = 1 << s->nbits;
+    for(j=0;j<np;j++) {
+        k = revtab[j];
+        if (k < j) {
+            tmp = z[k];
+            z[k] = z[j];
+            z[j] = tmp;
+        }
+    }
+}
+
+void fft_end(FFTContext *s)
+{
+    av_freep(&s->revtab);
+    av_freep(&s->exptab);
+    av_freep(&s->exptab1);
+}
+